(1) Field of the Invention
The present invention relates to a fixing device of an image forming apparatus utilizing the electrophotographic system or an electrostatic transfer system, such as a duplicator, a printer, a facsimile machine and a multifunction machine, and more specifically, it relates to a fixing device that fixes an image by using a flash lamp, and an image forming apparatus using the same.
(2) Description of the Related Art
In a printer that forms a toner image utilizing a dry electrophotographic system, an image is formed by transferring a toner in a powder form onto a recording medium, and the toner image on the recording medium is applied with fixing energy to melt the powder toner on the recording medium, whereby the toner image is fixed.
As a device for applying the fixing energy in a high-speed printer, particularly, such a flash fixing device is used that utilizes luminescent energy of a non-contact flash lamp capable of applying high energy without influence on delivery of the recording medium.
The flash lamp used in the flash fixing device is constituted by a glass lamp tube having an inert gas, such as xenon, sealed therein and electrodes on both ends thereof, and a trigger wire disposed in a linear form along the longitudinal outer surface of the lamp tube. A high voltage is applied between the electrodes of the lamp tube simultaneously with applying a high voltage to the trigger wire, so as to induce a discharge phenomenon between the electrodes to emit light from the flash lamp.
With increasing expectation of full-color printing with a high-speed printer due to the needs from the market, the toner attaching amount on a recording medium is necessarily increased based on such demands as “enhancement of the color gamut with color toners” and “realization of superposition printing with two or more colors”. According to the demand, the flash fixing device capable of applying high energy also suffers a severe problem in increase of the toner attaching amount for obtaining good fixing quality.
For example, in the case where full-color fixing is to be carried out under the fixing conditions for a monochrome toner in the conventional system, fixing failure occurs in a full-color part (which has a large toner attaching amount) due to shortage of energy.
In the case where large light energy is applied to toners in a short period of time, on the other hand, the components of the toner are sublimated to adversely affect the image.
Under the circumstances, there is a demand for a fixing method capable of favorably fixing a color image with a large toner attaching amount (i.e., the toner is melted to smoothen the fixed surface, and the fixing property is improved).